The general purpose of this proposed grant is to provide a firm understanding of the relationships between localization in space and speech reception, especially in conditions where backgroung noise or voices are present. Emphasis will be placed on the differences in binaural and monaural listening, the clues afforded by head movement and the azimuth position of the primary and interfering signal sources. The investigation described is divided into several experiments in order to explore systematically the important variables influencing binaural vs. monaural localization and speech reception. The magnitude and direction of head displacement during head movement conditions will be monitored on a head angle transducer system that is sensitive to movements in the horizontal plane. After obtaining data on normal and monaural hearing listeners, the results should be related to individuals with selected hearing impairments and to conditions where hearing aid amplification is utilized.